nsamp <- 1000
df <- data.frame(x1 = rnorm(nsamp,0,1),
x2 = rnorm(nsamp,0,1),
x3 = rnorm(nsamp,0,1))
linpred <- 1 + 2*df$x1 -0.18*df$x2 -3.5*df$x3
y <- rbinom(nsamp, 1, plogis(linpred))
df <- cbind(df, y)
mod1 <- glm(y~x1 +x2, data=df, family="binomial")
mod2 <- glm(y~x1 +x2 + x3, data=df, family="binomial")